=head1 NAME
-perldelta - what's new for perl v5.6.0
+perl56delta - what's new for perl v5.6.0
=head1 DESCRIPTION
-This document describes differences between the 5.005 release and this one.
+This document describes differences between the 5.005 release and the 5.6.0
+release.
=head1 Core Enhancements
=head2 Interpreter cloning, threads, and concurrency
-Perl 5.005_63 introduces the beginnings of support for running multiple
+Perl 5.6.0 introduces the beginnings of support for running multiple
interpreters concurrently in different threads. In conjunction with
the perl_clone() API call, which can be used to selectively duplicate
the state of any given interpreter, it is possible to compile a
# new features supported
}
-C<require> and C<use> also have some special magic to support such literals.
-They will be interpreted as a version rather than as a module name:
+C<require> and C<use> also have some special magic to support such
+literals, but this particular usage should be avoided because it leads to
+misleading error messages under versions of Perl which don't support vector
+strings. Using a true version number will ensure correct behavior in all
+versions of Perl:
- require v5.6.0; # croak if $^V lt v5.6.0
- use v5.6.0; # same, but croaks at compile-time
-
-Alternatively, the C<v> may be omitted if there is more than one dot:
-
- require 5.6.0;
- use 5.6.0;
+ require 5.006; # run time check for v5.6
+ use 5.006_001; # compile time check for v5.6.1
Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
to print ordinals of characters in arbitrary strings:
that with a C<use attrs> pragma in the body of the subroutine.
That can now be accomplished with declaration syntax, like this:
- sub mymethod : locked method ;
+ sub mymethod : locked method;
...
sub mymethod : locked method {
...
}
- sub othermethod :locked :method ;
+ sub othermethod :locked :method;
...
sub othermethod :locked :method {
...
NOTE: This is currently an experimental feature. Interfaces and
implementation are subject to change.
-=item Support for CHECK blocks
+=head2 Support for CHECK blocks
In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
subroutines named C<CHECK> are now special. These are queued up during
For example to match alphabetic characters use /[[:alpha:]]/.
See L<perlre> for details.
-=item Better pseudo-random number generator
+=head2 Better pseudo-random number generator
In 5.005_0x and earlier, perl's rand() function used the C library
rand(3) function. As of 5.005_52, Configure tests for drand48(),
now correctly prints "3|a", instead of "2|a".
-=item Better worst-case behavior of hashes
+=head2 Better worst-case behavior of hashes
Small changes in the hashing algorithm have been implemented in
order to improve the distribution of lower order bits in the
is destroyed and all the weak references to the object are
automatically undef-ed.
-To use this feature, you need the WeakRef package from CPAN, which
+To use this feature, you need the Devel::WeakRef package from CPAN, which
contains additional documentation.
NOTE: This is an experimental feature. Details are subject to change.
is pointing at, instead of always going to the underlying C runtime
library's C<stderr>.
-=item More consistent close-on-exec behavior
+=head2 More consistent close-on-exec behavior
On systems that support a close-on-exec flag on filehandles, the
flag is now set for any handles created by pipe(), socketpair(),
because other untrusted processes can modify messages and shared memory
segments for their own nefarious purposes.
-=item More functional bareword prototype (*)
+=head2 More functional bareword prototype (*)
Bareword prototypes have been rationalized to enable them to be used
to override builtins that accept barewords and interpret them in
This behavior must be specifically enabled when running Configure.
See F<INSTALL> and F<README.Y2K>.
+=head2 Arrays now always interpolate into double-quoted strings
+
+In double-quoted strings, arrays now interpolate, no matter what. The
+behavior in earlier versions of perl 5 was that arrays would interpolate
+into strings if the array had been mentioned before the string was
+compiled, and otherwise Perl would raise a fatal compile-time error.
+In versions 5.000 through 5.003, the error was
+
+ Literal @example now requires backslash
+
+In versions 5.004_01 through 5.6.0, the error was
+
+ In string, @example now must be written as \@example
+
+The idea here was to get people into the habit of writing
+C<"fred\@example.com"> when they wanted a literal C<@> sign, just as
+they have always written C<"Give me back my \$5"> when they wanted a
+literal C<$> sign.
+
+Starting with 5.6.1, when Perl now sees an C<@> sign in a
+double-quoted string, it I<always> attempts to interpolate an array,
+regardless of whether or not the array has been used or declared
+already. The fatal error has been downgraded to an optional warning:
+
+ Possible unintended interpolation of @example in string
+
+This warns you that C<"fred@example.com"> is going to turn into
+C<fred.com> if you don't backslash the C<@>.
+See http://www.plover.com/~mjd/perl/at-error.html for more details
+about the history here.
+
+=head2 @- and @+ provide starting/ending offsets of regex matches
+
+The new magic variables @- and @+ provide the starting and ending
+offsets, respectively, of $&, $1, $2, etc. See L<perlvar> for
+details.
+
=head1 Modules and Pragmata
=head2 Modules
=item B
The Perl Compiler suite has been extensively reworked for this
-release. More of the standard Perl testsuite passes when run
+release. More of the standard Perl test suite passes when run
under the Compiler, but there is still a significant way to
go to achieve production quality compiled executables.
=head1 NAME
- sample - Using GetOpt::Long and Pod::Usage
+ sample - Using Getopt::Long and Pod::Usage
=head1 SYNOPSIS
Minor changes in how subroutine calls are handled internally
provide marginal improvements in performance.
-=item delete(), each(), values() and hash iteration are faster
+=head2 delete(), each(), values() and hash iteration are faster
The hash values returned by delete(), each(), values() and hashes in a
list context are the actual values in the hash, instead of copies.
behavior, END blocks are not executed anymore when the C<-c> switch
is used, or if compilation fails.
-See L<CHECK blocks> for how to run things when the compile phase ends.
+See L</"Support for CHECK blocks"> for how to run things when the compile
+phase ends.
=head2 Potential to leak DATA filehandles
Remember that "my", "our", and "local" bind tighter than comma.
+=item Possible unintended interpolation of %s in string
+
+(W ambiguous) It used to be that Perl would try to guess whether you
+wanted an array interpolated or a literal @. It no longer does this;
+arrays are now I<always> interpolated into strings. This means that
+if you try something like:
+
+ print "fred@example.com";
+
+and the array C<@example> doesn't exist, Perl is going to print
+C<fred.com>, which is probably not what you wanted. To get a literal
+C<@> sign in a string, put a backslash before it, just as you would
+to get a literal C<$> sign.
+
=item Possible Y2K bug: %s
(W y2k) You are concatenating the number 19 with another number, which
that are comprised entirely of undefined values.
See L</"Behavior of list slices is more consistent">.
-=head2 Format of $English::PERL_VERSION is different
+=item Format of $English::PERL_VERSION is different
The English module now sets $PERL_VERSION to $^V (a string value) rather
than C<$]> (a numeric value). This is a potential incompatibility.
In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
-=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
+=item delete(), each(), values() and C<\(%h)>
+
+operate on aliases to values, not copies
-delete(), each(), values() and hashes in a list context return the actual
+delete(), each(), values() and hashes (e.g. C<\(%h)>)
+in a list context return the actual
values in the hash, instead of copies (as they used to in earlier
versions). Typical idioms for using these constructs copy the
returned values, but this can make a significant difference when
See L</"More functional bareword prototype (*)">.
-=head2 Semantics of bit operators may have changed on 64-bit platforms
+=item Semantics of bit operators may have changed on 64-bit platforms
If your platform is either natively 64-bit or if Perl has been
configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
See L</"Bit operators support full native integer width">.
-=head2 More builtins taint their results
+=item More builtins taint their results
As described in L</"Improved security features">, there may be more
sources of taint in a Perl program.
=head2 Compatible C Source API Changes
-=over
+=over 4
=item C<PATCHLEVEL> is now C<PERL_VERSION>
=item The DB module
-=item The regular expression constructs C<(?{ code })> and C<(??{ code })>
+=item The regular expression code constructs:
+
+C<(?{ code })> and C<(??{ code })>
=back
might directly modify logical name tables and introduce nonstandard names,
or it may indicate that a logical name table has been corrupted.
+=item In string, @%s now must be written as \@%s
+
+The description of this error used to say:
+
+ (Someday it will simply assume that an unbackslashed @
+ interpolates an array.)
+
+That day has come, and this fatal error has been removed. It has been
+replaced by a non-fatal warning instead.
+See L</Arrays now always interpolate into double-quoted strings> for
+details.
+
=item Probable precedence problem on %s
(W) The compiler found a bareword where it expected a conditional,
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc newsgroup.
-There may also be information at http://www.perl.com/perl/, the Perl
+There may also be information at http://www.perl.com/perl/ , the Perl
Home Page.
If you believe you have an unreported bug, please run the B<perlbug>
program included with your release. Be sure to trim your bug down
to a tiny but sufficient test case. Your bug report, along with the
-output of C<perl -V>, will be sent off to perlbug@perl.com to be
+output of C<perl -V>, will be sent off to perlbug@perl.org to be
analysed by the Perl porting team.
=head1 SEE ALSO
Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
contributions from The Perl Porters.
-Send omissions or corrections to <F<perlbug@perl.com>>.
+Send omissions or corrections to <F<perlbug@perl.org>>.
=cut
https://perl5.git.perl.org / perl5.git / blobdiff